Present day manufacturing of an optical disc such as a DVD (sometimes referred to as a digital versatile disc or a digital video disc) begins with the creation of a glass master, which includes providing a layer of photoresist on a piece of ground, optically polished glass. A laser selectively exposes the photoresist to create a pattern of pits and lands, corresponding to a pattern of binary “ones” and “zeros” representing the digital information carried by the finished DVD. The exposed pattern of photoresist is developed to yield a pit and land structure of photoresist on the glass master.
The glass master undergoes a series of copy transformations (negative to positive to negative) to yield one or more stampers bearing the pit and land structure. The stamper is used during an injection molding process to create a polycarbonate layer or substrate having a topography that mirrors that of the stamper. The patterned polycarbonate layer undergoes metallization, which provides a reflective layer for use in reading the data. In the case of a single-sided, single layer disc, the metalized polycarbonate layer is bonded to a blank layer or substrate, e.g., as a protective layer, to yield the final disc, such as a DVD-5.
In the case of dual layer DVDs, each of the two data layers (referred to as a L0 layer and L1 layer, respectively) has an associated metal-containing layer for reflecting a laser beam used for reading the data. The first metal-containing layer associated with the first data layer is partially reflective, which allows a portion of a laser beam to pass through for accessing the data on the second data layer. The second metal-containing layer associated with the second data layer is usually totally reflective.